An apparatus is known which is mounted on a hybrid vehicle provided with a generator for generating electricity using engine power, and a battery (a storage battery) charged by the generator, and which is configured to control the charge and discharge of the battery such that a state of charge (SOC) of the battery is a target SOC (e.g. refer to Patent documents 1 and 2).
For example, Patent document 1 discloses that a used percentage of the SOC of a battery is expanded and the battery is efficiently used by changing the target SOC, as occasion demands, on the basis of an average charge and discharge amount of the battery. For example, Patent document 2 discloses that charge and discharge control is performed in view of dispersion of the amount of electricity stored in the battery. In addition, as a prior art document related to the present invention, there is Patent document 3.